CN115697755A - Energy storage system for load handling devices - Google Patents

Abstract

The present invention is a load handling device (30) for lifting and moving one or more containers (10) stacked in a storage system comprising a grid frame (14) supporting passageways arranged in a grid pattern above a stack (12) of said containers (10), the load handling device (30) comprising: i) A carrier body (32), the carrier body (32) housing a drive mechanism, the drive mechanism being operably configured to move the load handling device (30) on the grid frame (14); ii) lifting means comprising a lift drive assembly and a gripper (39), the gripper (39) being configured, in use, to releasably grip the container (10) and lift the container (10) from the stack (12) into the container receiving space (40); wherein the lift drive assembly and/or the drive mechanism comprises at least one motor constituting an electrical load (104); iii) A rechargeable power supply (100); iv) an assembly of one or more supercapacitor modules (102); characterized in that an electrical load (104) is connected across the assembly of one or more super capacitor modules (102) and a rechargeable power supply (100) is connected in parallel to the assembly of one or more super capacitor modules (102) such that the rechargeable power supply (100) is configured to power the assembly of one or more super capacitor modules (102).

Description

Energy storage system for load handling devices

technical field

The present invention relates to the field of load handling devices for handling storage containers or boxes in stores comprising grids of stacked containers, and in particular to energy storage systems for load handling devices.

Background technique

Storage systems comprising a three-dimensional storage grid structure and storage containers/cases stacked on top of each other within the storage system are known. PCT International Application No. WO2015/185628A filed by Ocado Corporation describes a known storage and fulfillment system in which stacks 10 of boxes or containers are arranged within a grid frame structure. Boxes or containers are accessed by load handling units operating on rails located on top of the lattice frame structure. Figures 1-3 schematically illustrate this type of system. As shown in FIGS. 1 and 2 , a stackable container, referred to as a case 10 , is stacked on top of another stackable container to form a stack 12 . The stack 12 is arranged in a grid frame structure 14 in a warehouse or manufacturing environment. The grid framework consists of a plurality of storage columns or grid columns. Each grid in the grid frame structure has at least one grid column for storing stacks of containers. FIG. 1 is a schematic perspective view of a lattice frame structure 14 and FIG. 2 is a top view of a stack 12 of boxes 10 disposed within the frame structure 14 . Each box 10 usually contains a plurality of product items (not shown) and the product items in the box 10 can be of the same product type or of different product types, depending on the application scenarios. The lattice frame structure 14 includes a plurality of vertical members 16 supporting horizontal members 18 , 20 . The first set of parallel horizontal members 18 is arranged 25 perpendicular to the second set of parallel horizontal members 20 to form a plurality of horizontal grid structures comprising a plurality of grid cells 23 supported by the vertical members 16 . The members 16, 18, 20 are typically made of metal. Boxes 10 are stacked within grid cells 23 between members 16 , 18 , 20 of grid frame structure 14 such that grid frame structure 14 prevents horizontal movement of stack 12 of boxes 10 and guides vertical movement of boxes 10 .

The top layer of the grid frame structure 14 includes rails 22 arranged in a grid pattern comprising a plurality of grid cells 23 spanning the top of the stack 12 . Referring additionally to FIG. 3 , the track 22 supports a plurality of load handling devices 30 . A first set 22a of parallel tracks 22 guides the automatic load handling device 30 to move across the top of the grid frame structure 14 in a first direction (e.g., the X direction), and a second set 22b of parallel tracks 22 is arranged perpendicular to the first set 22a and guide the load handling device 30 to move along a second direction (eg, Y direction) perpendicular to the first direction. In this way, the rails 22 enable two-dimensional lateral movement of the automated load handling device 30 in the horizontal X-Y plane so that the load handling device 30 can be moved into position above any of the stacks 12 . The known load handling device 30 shown in Figures 4 and 5 comprises a carrier body 32 which is described in PCT International Application No. WO2015/019055 filed by Ocado Corporation, which is incorporated herein by reference. The International Application incorporates the present invention wherein each load handling device 30 covers only one grid space or grid cell 23 of the grid frame structure 14 . Here, the load handling device 30 includes a wheel assembly comprising a pair of wheels at the front of the vehicle body 32 and a pair of wheels 34 at the rear of the vehicle 32 for use with the first set of wheels. The track or track engages a first set of wheels 34 for guiding movement of the device in a first direction, and a pair of wheels 36 on each side of the carrier 32 for engaging a second set of track or track for A second set of wheels 36 guides movement of the device in a second direction. Each set of wheels is driven by one or more motors to enable the vehicle to move along the track in X and Y directions respectively. One or two sets of wheels can be moved vertically to lift each set off its respective track so that the vehicle can move in a desired direction.

While Figures 4 and 5 illustrate load handling devices occupying a single grid space, where the container receiving space is a depression inside the carrier body, the invention also encompasses load handling devices that include a cantilever as part of the carrier body, The container storage space is located under the cantilever.

The load handling unit 30 is equipped with a lifting device or hoisting mechanism driven by one or more motors to lift storage containers, which may weigh up to 30 kilograms, from above. The lifting mechanism includes a winch tether or cable 38 and a grip arrangement 39 wound on a reel or reel (not shown). The lifting device includes a group of lifting tethers 38 extending vertically and connected to the four corners of the lifting frame 39 or near the four corners. each of the four corners) for releasably connecting to the storage container 10. The gripping device 39 is configured to releasably grasp the top of the storage container 10 to lift it from a stack of containers in a storage system of the type shown in FIGS. 1 and 2 .

Wheels 34, 36 are provided in the lower half around the outer rim of the cavity or recess (referred to as the container receiving recess). The recess is sized to accommodate the container 10 when it is lifted by the lifting mechanism as shown in Figures 5a and 5b. While in the recess, the container is lifted off the track below so that the carrier can be moved laterally to a different location. On reaching a target location, such as another stack, an access point in a storage system or a conveyor belt, the case or container can be lowered from the container receiving section and released from the gripping device.

Although not shown in FIGS. 1-3, the load processing device 30 is powered by an on-board rechargeable power source during operation. One common type of rechargeable power source is a battery. Examples of rechargeable batteries are lithium ion batteries, nickel cadmium batteries, nickel metal hydride batteries, lithium ion polymer batteries, thin film batteries, and smart batteries carbon foam based lead acid batteries.

The technical advantage of batteries is their high energy density, i.e. their high capacity to store energy per unit mass, making them suitable for use in mobile applications such as load handling units, as they store enough energy to last long periods of time between charges Power the unit. They have a low self-discharge rate so they retain enough power to continue operating after a certain period of downtime. However, the low power density of batteries makes them ill-suited to handle high acceleration demands and are limited in how much regenerative energy they can extract from deceleration events. Also, in battery tools means excessive battery cycling converts some of the electrical energy into heat, thus wasting energy at low temperatures is also a problem.

Other disadvantages of batteries are that they are heavy, expensive, suffer from resistive power loss, take a long time to charge, have limited charge-discharge cycle life and decay over time. A low charging rate means that the battery loses operating time while it is charging. The limited number of charge and discharge cycles means that the battery has a short lifespan and needs to be replaced frequently.

An alternative to battery technology is supercapacitors. Supercapacitors have high power density, making them suitable for applications with high acceleration requirements (short duration of high power consumption) and can also harvest regenerative energy from deceleration events (short duration of high power input). The advantage of supercapacitors over batteries is that they are lighter, more efficient, charge faster and can perform a greater number of charge and discharge cycles with less decay over time. Fast charging means less downtime. The main disadvantages of supercapacitors compared to batteries are their high self-discharge rate (so they may not retain enough charge to continue operating after a period of non-use) and lower energy density.

Figure 6 is an energy comparison Ragone plot that plots power density versus energy density and shows the relative positions of different types of energy storage devices. From this figure it can be seen that supercapacitors (labeled EDLC (Electric Double Layer Capacitor) on Figure 6) have low energy density but high power density, while Li-ion batteries have relatively high energy density but relatively low power density.

Table 1 compares some properties of batteries and supercapacitors.

Table 1: Comparison of properties of batteries and supercapacitors

Prior art load handling devices, such as those disclosed in PCT International Application with International Publication No. WO2015/019055, have all the problems of rechargeable batteries described above while having the advantage of high energy density.

The international application WO2020169474A1 of AutoStore discloses a container handling vehicle powered by first and second rechargeable power sources, specifically a rechargeable battery and a supercapacitor. It has some advantages of supercapacitors, but still suffers from the disadvantages of battery attenuation and wasted energy heating.

GB2006089.3 discloses a load handling device in which the main power supply is a supercapacitor and a DC-DC converter is used to vary the voltage. It has the advantages of the supercapacitor mentioned above, but since the supercapacitor is the only power source, the load processing device has the disadvantages of low energy density and high self-discharge rate.

This application is directed to British patent application No. GB2006089.3 filed on April 24, 2020, British patent application No. GB2010704.1 filed on July 10, 2020, and No. GB2020583.7 filed on December 23, 2020 Priority is claimed from UK patent applications, the contents of which are hereby incorporated by reference into the present application.

Contents of the invention

The present invention is a load handling apparatus for lifting and moving one or more containers stacked in a storage system comprising a grid frame supporting pathways arranged in a grid pattern above the stack of containers, the load handling apparatus comprising :

i) a carrier body housing a drive mechanism operatively arranged to move the load handling device on the grid frame;

ii) lifting means comprising a lifting drive assembly and gripper means configured, in use, to releasably grasp the container and lift the container from the stack into the container receiving space; wherein the lifting drive assembly and/or or the drive mechanism includes at least one motor constituting an electrical load;

iii) rechargeable power source;

iv) Assemblies consisting of one or more supercapacitor modules;

It is characterized in that the electric load is connected across the two ends of the assembly composed of one or more supercapacitor modules, and the rechargeable power supply is connected in parallel to the assembly composed of one or more supercapacitor modules so that the rechargeable power supply is configured to A component composed of one or more supercapacitor modules supplies power.

For ease of reference, "a component composed of one or more supercapacitor modules" and "supercapacitor" will be used interchangeably when describing the present invention. When referring to supercapacitors, it should be understood that the term covers assemblies of supercapacitor modules connected in series and/or in parallel.

A common problem with load handling devices, especially where the rechargeable power source is a rechargeable battery, is that the battery is subjected to frequent charge and discharge cycles from the electrical load due to acceleration and operation of the lift drive assembly and/or drive mechanism. This puts rechargeable batteries under enormous stress due to the battery's internal resistance causing the battery to heat up during charge and discharge cycles. Charge-discharge cycling can cause premature battery aging, requiring more frequent battery replacement.

In order to overcome this problem, the rechargeable power supply in the present invention is mainly used to supply power to one or more supercapacitor modules, instead of directly supplying power to electric loads. Compared to rechargeable batteries, supercapacitors are better able to accommodate charge and discharge cycles from electrical loads, and are therefore able to withstand surges in power consumption as load processing devices accelerate across the grid. The combination of a rechargeable battery and one or more supercapacitor modules provides a hybrid system with high power density and high energy density, combining the advantages of batteries and supercapacitors. The rechargeable power supply can stabilize and constant current to supply power to components composed of one or more supercapacitor modules, thereby avoiding the damaging effect of frequent charging and discharging cycles.

An advantage of the present invention over prior art load handling devices is that the lifetime of the rechargeable power supply is extended, thereby reducing operating costs and downtime.

The load processing device may further include a load DC-DC converter between the assembly consisting of one or more supercapacitor modules and the electrical load. The load DC-DC converter between the component composed of one or more supercapacitor modules and the electric load may be a boost converter.

The load processing device may further include a source DC-DC converter between the rechargeable power source and the assembly consisting of one or more supercapacitor modules. The source DC-DC converter between the rechargeable power source and the assembly consisting of one or more supercapacitor modules can be a buck converter.

The controller may be configured to vary the power provided from the rechargeable power source to the assembly of one or more ultracapacitor modules. The controller may be configured to instruct the rechargeable power source to supply power to the assembly of one or more supercapacitor modules when the voltage of the assembly of one or more supercapacitor modules is below a predetermined supercapacitor target voltage threshold. The predetermined supercapacitor target voltage threshold may be lower than the maximum rated voltage of an assembly of one or more supercapacitor modules. The controller may be configured to instruct the rechargeable power source to power the assembly of one or more supercapacitor modules at a predetermined threshold current for battery balancing. The controller may be configured to disconnect the rechargeable power source from the assembly of the one or more supercapacitor modules such that the rechargeable power source experiences a period of low current consumption during which no power is supplied to the battery powered by the one or more supercapacitor modules. Components composed of supercapacitor modules.

The load handling device may further include energy recovery circuitry to transfer energy regenerated from the drive mechanism and/or lifter assembly to the assembly of one or more ultracapacitor modules. The energy recovery circuit may include diodes or transistors.

An assembly of one or more supercapacitor modules can have a lower internal impedance than a rechargeable power source.

The electrical load may include a first portion and a second portion, wherein the first portion of the electrical load may include a powered load and the second portion of the electrical load may include a non-powered load. The rechargeable power source can be configured to provide power to non-motive loads.

An assembly of one or more supercapacitor modules can be configured as a main power source for a load processing device, while a rechargeable power source can be configured as an auxiliary power source. The controller may be configured to instruct the rechargeable power source to provide backup power to the electrical load when the voltage across the assembly of one or more ultracapacitor modules is below a predetermined ultracapacitor voltage threshold.

An assembly of one or more supercapacitor modules may be distributed around the outside of the container receiving recess in the carrier body of the load handling device and between the outer and inner walls of the load handling device.

An assembly composed of one or more supercapacitor modules may include capacitors, supercapacitors, ultracapacitors, lithium capacitors, electrochemical double layer capacitors, electric double layer capacitors, pseudocapacitors or hybrid capacitors.

Rechargeable power sources can include lithium-ion batteries, lithium-ion polymer batteries, lithium-air batteries, lithium-iron batteries, lithium iron phosphate batteries, lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, sodium-ion batteries, sodium Air battery, thin film battery or smart battery carbon foam based lead-acid battery.

Another aspect of the invention is a storage system comprising a grid frame arranged in a grid pattern supported above a stack of containers and a plurality of load handling devices as defined in the invention. The storage system may further include one or more supercapacitor charging stations located at grid locations above the access points, wherein during the raising or lowering operation one of the one or more supercapacitor charging stations is the load handling device Components consisting of one or more supercapacitor modules are charged. The one or more supercapacitor charging stations may be high rate inductive supercapacitor charging stations. A controller on the load processing device may be configured to instruct the assembly of one or more ultracapacitor modules to charge the rechargeable power source. The controller may be configured to instruct one or more ultracapacitor modules to power the rechargeable power source at a predetermined threshold current for battery balancing. One or more supercapacitor charging stations may enable the load processing device to maintain the voltage level of the rechargeable power source above a predetermined threshold voltage for powering the electrical load.

Another aspect of the invention is a fulfillment center comprising the storage system described herein. The temperature within the fulfillment center may be any of the following: ambient temperature at or above 4°C; refrigerated temperature from approximately 0° to approximately 4°C; or approximately -25°C to approximately 0°C freezing temperature.

Connecting supercapacitors between rechargeable sources and electrical loads enables energy storage systems to enjoy the advantages of high energy density and high power density while mitigating their disadvantages. This is especially true when the rechargeable battery is a high energy density battery. Supercapacitors are subjected to charge and discharge cycles due to the acceleration/deceleration demands of the electrical load, protecting the battery from these cycles, thereby improving battery life. Improved battery life results in lower operating costs and less downtime because batteries do not have to be replaced as frequently. Fewer battery cycles means less battery energy loss and less active energy dissipated as heat. This is especially important when load handling units operate in refrigerated or frozen cargo fulfillment centers where temperatures are kept low. In this case, not only does the heat release from the load handling means represent a waste of energy, but a greater energy consumption is required to maintain the low temperature in the travel center.

Description of drawings

Further features of the present invention will be clarified through the following detailed description of specific embodiments exemplified in conjunction with the accompanying drawings.

1 is a schematic diagram of a grid frame structure according to a known system.

FIG. 2 is a schematic diagram showing a top view of a stack of boxes disposed within the frame structure shown in FIG. 1 .

Figure 3 is a schematic diagram of a known system of load handling devices operating on a lattice frame structure.

Figure 4 is a schematic perspective view of a load handling device showing a lifting device grasping a container from above.

Figures 5(a) and 5(b) are schematic perspective cutaway views of the load handling device of Figure 4, showing (a) the container storage space of the load handling device and (b) contained within the container storage space of the load handling device container.

Figure 6 is an energy comparison Lagon diagram showing the energy density and power density of different energy storage devices.

Fig. 7 is a circuit diagram showing a rechargeable power source and a supercapacitor connected in parallel with an electrical load.

Figure 8 is a circuit diagram highlighting the source DC-DC converter between the rechargeable power source and the supercapacitor and the load DC-DC converter between the supercapacitor and the electrical load.

Figure 9 is a circuit diagram highlighting the buck and boost DC-DC converters.

FIG. 10 is a schematic diagram of a PID controller for a boost converter.

Figure 11 is a circuit diagram highlighting the energy recovery circuitry for directing recovered energy into a supercapacitor.

Figure 12 is a circuit diagram highlighting a non-motive electrical load drawing power from a rechargeable power source.

Figure 13 is a circuit diagram illustrating the direction of current flow during a deceleration event.

14 is a circuit diagram illustrating the direction of current flow when the rechargeable power source is charging the supercapacitor during a deceleration event.

Fig. 15 is a circuit diagram showing the direction of current flow in the idle state of the load processing device.

FIG. 16 is a circuit diagram showing the direction of current flow when the rechargeable power supply is charging the supercapacitor when the load processing device is idle.

17 is a circuit diagram illustrating the direction of current flow in a load handling device during an acceleration event.

18 is a circuit diagram illustrating the direction of current flow when the rechargeable power source is charging the supercapacitor during an acceleration event in the load processing device.

Figure 19 illustrates the transient currents caused by lowering and raising the gripper when stacking and retrieving storage containers.

20 is a schematic diagram of the load handling device showing the gap between the inner and outer walls of the carrier body.

21 is a schematic diagram of a load handling device showing supercapacitor modules distributed in the gap between the inner and outer walls of the carrier body.

Figure 22 compares charge voltage and status from battery voltage measurements, manufacturer data, and battery fuel gauges.

Figure 23 shows how the battery fuel gauge measurement becomes inaccurate after a period of continuous operation.

24 is a circuit diagram showing a rechargeable power supply connected in parallel with an electrical load and a filter circuit.

Figure 25 is a circuit diagram showing a rechargeable power supply connected in parallel with an electrical load and a filtering circuit with a filtered DC-DC converter located between the filtering circuit and the electrical load.

Figure 26 is a circuit diagram showing a rechargeable power source connected in parallel with an electrical load and a filter circuit, where the filter DC-DC converter is located between the filter circuit and the electrical load, and the source DC-DC converter is located between the rechargeable power source and the filter circuit between.

Figure 27 shows some specific implementations of filter circuits: a) RC circuit; b) RL circuit; c) RLC circuit; d) Butterworth filter; e) active filter circuit using operational amplifier.

Figure 28 shows the voltage boost of an op amp plotted against frequency.

Figure 29 illustrates the transient currents caused by lowering and raising the gripper when stacking and retrieving storage containers.

Figure 30 shows the Fourier transform of the current flowing through the rechargeable power supply.

Figure 31 shows a simulation model of a simple RC circuit.

Figure 32 shows a) the same load current as in Figure 29; b) the current with a 20Hz filter circuit; c) the current with a 7Hz filter circuit.

Figure 33 compares a) load current with current with 20Hz filter circuit; b) load current with current with 7Hz filter circuit.

Figure 34 shows the discharge curve of a Li-ion battery.

Figure 35 shows the shape of the discharge curves for batteries and supercapacitors.

Figure 36 illustrates the power requirements of a load handling device as it moves across the storage grid.

FIG. 37 shows a simple circuit diagram of a supercapacitor 102 connected in parallel with a rechargeable power source 100 .

Figure 38 shows a multi-cell battery connected in series with supercapacitor assemblies connected in parallel with multiple electrical loads.

Figure 39 shows a circuit diagram of a controller directing charge from a rechargeable source to a supercapacitor.

Figure 40 shows the circuit diagram of the controller directing the recovered energy to the super capacitor.

Figure 41 is an enlarged view of one embodiment of a controller and DC-DC converter.

Figure 42 shows the super capacitor protection circuit.

Detailed ways

Rechargeable power source configured to power an assembly of one or more supercapacitor modules

FIG. 7 is a circuit diagram showing a rechargeable power source 100 connected in parallel with an ultracapacitor 102 and an electrical load 104 . The electrical load 104 may include one or more motors that move the vehicle on rails in the X and Y directions, respectively, through the sets of drive wheels 34 and 36 and/or drive a lifting device or lifting mechanism to lift one or more of the storage containers from above. more than one engine. The super capacitor 102 is connected between the rechargeable power source 100 and the electric load 104, which allows the rechargeable power source to provide power to the super capacitor or receive power from the super capacitor, and the super capacitor can provide power to the power load or receive power from the power load .

For convenience of illustration, the circuit diagram of FIG. 7 shows the rechargeable power supply 100 as a single battery unit, and the supercapacitor 102 as a single supercapacitor. It should be understood that rechargeable power sources are not limited to batteries, and that batteries may include assemblies of one or more cells, rather than just a single cell.

Similarly, supercapacitor 102 may comprise an assembly of one or more supercapacitor modules, rather than just a single supercapacitor module.

DC-DC Converter

The circuit may additionally include a source DC-DC converter 108 between the rechargeable power source 100 and the super capacitor 102 . The purpose of the source DC-DC converter is to convert the voltage across the rechargeable power source to a different voltage across the supercapacitor.

The source DC-DC converter 108 between the rechargeable power source 100 and the ultracapacitor 102 may comprise a step-up converter or a step-down converter. Preferably, the source DC-DC converter 108 between the rechargeable power source 100 and the super capacitor 102 may comprise a boost converter. The advantage of a higher voltage across the supercap is that the supercap can store more energy. Additionally, higher voltages (and thus lower currents) result in lower resistive power losses (P=I^2R) and thus reduce the amount of effective energy converted to heat.

The circuit may additionally include a load DC-DC converter 110 between the ultracapacitor 102 and the electrical load 104 . The purpose of the load DC-DC converter 108 between the rechargeable power source 100 and the supercapacitor 102 is to convert the voltage across the supercapacitor to a different voltage across the electrical load.

The load DC-DC converter 110 between the ultracapacitor 102 and the electrical load 104 may comprise a step-up converter or a step-down converter.

FIG. 8 is a circuit diagram showing the source DC-DC converter 108 between the rechargeable power source 100 and the supercapacitor 102 and the load DC-DC converter 110 between the supercapacitor 102 and the electrical load 104 . It should be understood that although FIG. 8 shows two DC-DC converters, the present invention encompasses circuits including source DC-DC converter 108 but not load DC-DC converter 110, as well as circuits including load DC-DC converter 110. 110 but not including the circuitry of the source DC-DC converter 108.

Preferably, the source DC-DC converter 108 between the rechargeable power source 100 and the supercapacitor 102 is a digitally controlled boost converter, and the source DC-DC converter 110 between the supercapacitor 102 and the electrical load 104 is a step-down converter. pressure converter. Fig. 9 shows that the source DC-DC converter 108 between the rechargeable power source 100 and the supercapacitor 102 is a boost converter, and the load DC-DC converter 110 between the supercapacitor 102 and the electrical load 104 is a buck converter The circuit diagram for the case. The controller 114 may be used to minimize current from the rechargeable power source while maintaining the ultracapacitor voltage within a desired range.

The advantage of the source DC-DC converter 108 between the rechargeable power source 100 and the super capacitor 102 being a boost converter is that the voltage of the super capacitor will never drop below the rechargeable power source voltage. The load DC-DC converter can thus be powered by a simple buck converter to power the electrical load 104 . Energy recovered from the deceleration time may be directed to the supercapacitor through the energy recovery circuit 112 . The circuit can be as simple as a power diode controlling the flow of current from an electrical load to a supercapacitor.

Controlling the charging of supercapacitors

An important issue to consider is how to control the state of charge of the supercapacitor. If the supercap is to be fully charged, the energy recovered will not be able to be stored in the supercap after a deceleration event. In this case, the recovered energy would need to be directed to the rechargeable power source (which would age the battery if the rechargeable power source is a battery) or dissipated as heat.

Figure 10 shows a possible embodiment of the controller 114 as a PID controller. One option for the controller 114 is to allow the rechargeable power source to charge the supercapacitor only when the supercapacitor's power is below a predetermined supercapacitor target voltage threshold. This can be achieved by measuring the voltage Vc across the supercapacitor and allowing the rechargeable power source to charge the supercapacitor when the voltage on the supercapacitor is below a predetermined supercapacitor target voltage threshold. The predetermined supercapacitor target voltage threshold Vr is compared to the instantaneous supercapacitor voltage Vc, and the controller 114 adjusts its output accordingly.

energy recovery

During a deceleration event, kinetic energy can be recovered from the deceleration of the load handling device and stored in an ultracapacitor for later use.

The energy storage system of the load handling device must be able to receive power from the drive mechanism during a deceleration event in which the load handling device decelerates from its maximum velocity in the X or Y direction until it stops in a different grid position. The drive mechanism may include one or more electric motors that act as generators during deceleration events to convert the kinetic energy of the load handling device into electrical energy, which may be stored in an ultracapacitor for later use.

The energy storage system of the load handling device must be able to receive power from the lifting mechanism during a deceleration event in which the gripper device is lowered to a lower vertical position in the storage grid. As the gripper is lowered, the potential energy from its higher vertical initial position is converted into kinetic energy. The lift drive assembly may include one or more electric motors that act as generators during deceleration events to convert the kinetic energy of the load handling device into electrical energy, which may then be stored in an ultracapacitor for later use.

It will be appreciated that in the lowering operation, more energy can be recovered when the gripper device grips the storage container, since the mass of the storage container means more energy from the higher vertical initial position of the gripper device and storage container The most important thing is that energy can be recycled.

The recovered energy may be transferred into the supercapacitor 102 through the energy recovery circuit 112 as shown in FIG. 11 . The purpose of the energy recovery circuit 112 is to direct current into the supercapacitor 102 . This is beneficial because the recovered energy directed into the rechargeable source increases the number of charge and discharge cycles and accelerates battery aging if the rechargeable source is a battery. The energy recovery circuit may include one or more diodes or transistors.

An assembly of one or more supercapacitor modules may have a lower internal resistance than the rechargeable power supply, thereby ensuring that recovered energy is directed into the supercapacitor rather than into the rechargeable power supply.

Sizing supercapacitors to receive and store recovered energy

The predetermined supercapacitor target voltage threshold may be selected such that it is lower than the maximum rated voltage of the supercapacitor and such that the voltage difference between the predetermined supercapacitor target voltage threshold and the maximum rated voltage of the supercapacitor is sufficient for the supercapacitor to withstand one or more deceleration events recovered energy. Additionally, the power rating of the ultracapacitor may be selected such that the power rating is sufficient to receive power from a deceleration event.

The assembly of supercapacitor modules may be sized such that the voltage differential between a predetermined supercapacitor target voltage threshold and the supercapacitor's maximum rated voltage is sufficient to receive and store energy from a deceleration event.

Alternatively, the assembly of supercapacitor modules may be sized such that the voltage differential between a predetermined supercapacitor target voltage threshold and the supercapacitor's maximum rated voltage is sufficient to receive and store energy from a plurality of deceleration events. For example, if a load handling unit needs to move along the Y direction to a different grid cell and stack storage containers, the operation includes four acceleration/deceleration events: acceleration in the Y direction to maximum velocity (acceleration event); deceleration in the Y direction to dock above the target grid unit (deceleration event); lower the gripper and storage container from the container receiving space of the load handler to a lower vertical position for stacking the storage container (deceleration event); and raise the gripper upward Back to the load handler (acceleration event). There are two consecutive deceleration events in this time series. Dimensioning an assembly of one or more supercapacitor modules such that the voltage difference between the predetermined supercapacitor target voltage threshold and the supercapacitor's maximum rated voltage is sufficient to receive and store energy from both deceleration events means that the supercapacitor It can be used for this operation by itself, thereby reducing the number of power cycles required by the rechargeable power source and potentially extending its life. In general, it is an advantage that the energy capacity of the supercapacitor is sufficient for more than a typical deceleration event, so that the rechargeable power supply does not need to receive energy from an acceleration event during normal operation. Reversing the direction of current flow through a rechargeable source can speed up the aging process and reduce its lifespan, especially if the rechargeable source is a battery.

It is advantageous to size the supercapacitor so that the voltage difference between the predetermined supercapacitor target voltage threshold and the supercapacitor's maximum rated voltage is sufficient to receive and store energy from multiple deceleration events, as it ensures that even if an unexpectedly high During deceleration events, the energy flow between the rechargeable power source and the supercap still only goes in one direction during normal operation on the grid. Supercapacitors effectively cycle charge and discharge from acceleration/deceleration events, protecting the rechargeable power source from the aging effects of these cycles. The rechargeable power supply only needs to provide a constant "top-up" of energy to the supercapacitor at low power, without going through all the Charge-discharge cycle for acceleration/deceleration events. This has the added advantage of making it easier to provide a smooth and constant current profile to the rechargeable power supply.

If the source DC-DC converter 108 between the rechargeable power source and the super capacitor is a boost converter, then the predetermined super capacitor target voltage threshold may be higher than the voltage of the rechargeable power source. The advantage of this is that the supercapacitor 102 can store more capacity because the energy storage capacity is proportional to the square of the voltage.

One option is to set the minimum voltage of the super capacitor to be no lower than the voltage of the rechargeable power source. This has the advantage that the load DC-DC converter 110 can be a simple buck converter powering the electrical load 104 . Additionally, the energy recovery circuit 112 can remain as simple as a power diode if the voltage of the super capacitor is not lower than the voltage across the electrical load. The disadvantage of this option is that only a part of the voltage range of the super capacitor can be utilized.

Allowing the voltage of the supercapacitor to drop below the voltage of the rechargeable source, while doing so allows a greater range of the supercapacitor to be utilized, means that more complex electronics are required between the rechargeable source and the supercapacitor than Simple boost converter. In addition, if the voltage of the super capacitor is lower than the voltage across the electrical load, the energy recovery circuit 112 will need to become more complex to avoid over voltage of the super capacitor. Voltages beyond the supercapacitor's maximum rating will reduce the unit's operational life and eventually lead to failure.

For example, if the voltage of the rechargeable power source and the electrical load are both nominally 48V, then the predetermined supervoltage target voltage threshold may be set to 60V. The supercapacitor can be chosen such that the maximum voltage rating is 72V so that the supercapacitor will have sufficient energy storage capacity to store the energy recovered from the deceleration event. If the supercapacitor voltage is below 60V, the controller will allow the rechargeable power source to charge the supercapacitor. If the supercapacitor voltage is higher than 60V, the controller 114 will not allow the rechargeable power source to charge the supercapacitor. The supercap will provide energy for the acceleration event until the voltage drops below 60V, after which the controller will allow the rechargeable source to recharge the supercap. In order to simplify the electronic structure required in the source DC-DC converter 108 and the energy recovery circuit 112 , the supercapacitor 102 can be limited to operate above a minimum operating voltage of 48V.

Non-powered electrical loads

Electrical loads may include powered and non-powered electrical loads. Dynamic electrical loads are due to the demands of the drive mechanism and/or lift drive assembly and will vary based on the movement of the load handling device. Non-powered electrical loads are electrical loads used for any function other than movement of load handling devices, and may, for example, include electrical power used to communicate with the storage grid control system. These non-motive electrical loads always exist independently of the movement of the load handling device. FIG. 12 shows a circuit diagram of a non-motive electrical load 106 . Non-motive electrical loads can be powered by the rechargeable power source 100 .

Design the size of the supercapacitor to accelerate the event

The energy storage system of the load handling device must be able to power the drive mechanism to enable the load handling device to move in the X and Y directions on the grid. Movement in the X or Y direction includes an acceleration event in which the load handling device starts from docking and accelerates until it reaches a maximum velocity, followed by a deceleration event in which the load handling device decelerates from the maximum velocity until it docks at a different grid location. Each acceleration event is roughly followed by a deceleration event.

The energy storage system of the load handling unit must be able to provide power to enable the lift drive assembly to raise and lower the gripper unit to retrieve or stack storage containers. The lift operation consists of a deceleration event in which the gripper is lowered from the load handler to a lower vertical position within the grid frame, and the subsequent gripper grips the storage container and raises it vertically upward into container storage in the load handler Accelerating events in space. Similarly, a stacking operation consists of the lowering of the gripper device holding the storage container from the load handling device to a lower vertical position within the grid frame where the storage container is stacked, and the subsequent acceleration event of the gripper being raised vertically upwards to the load handling device . Each deceleration event is roughly followed by an acceleration event.

An assembly of ultracapacitor modules can be sized such that the power rating is sufficient to power an acceleration event.

Alternatively, an assembly of ultracapacitor modules may be sized such that the rated power is sufficient to power multiple acceleration events. For example, if a load handling unit needs to retrieve a storage container and move it to a different grid cell in the X direction, then this operation consists of four acceleration/deceleration events: lowering the gripper (deceleration event); raising the gripper; Hand device and storage container to put the storage container into the container storage space (acceleration event); accelerate to maximum velocity in the X direction (acceleration event); and decelerate to stop above the target grid cell (deceleration event). In this sequence of events there are two consecutive acceleration events. Sizing an assembly of one or more supercapacitor modules such that the power rating is sufficient to power both acceleration events means that the supercapacitor itself can be used for this operation, reducing the number of power cycles required by the rechargeable power source and May extend the life of the rechargeable power source. In general, it is an advantage that the power of the supercapacitor is sufficient for more than one typical acceleration event, so that the rechargeable power supply does not need to power the acceleration event during normal operation, but only needs to replenish the supercapacitor when the charge drops below a specified level. The rechargeable power source will still be immune to power cycling if there is an unexpectedly high acceleration.

The supercapacitors can be sized to have sufficient power and energy available to complete the most energy-demanding acceleration event, which may be movement in the X or Y direction across the entire storage grid.

circuit operation

Figures 13-18 illustrate the circuit operation of the load handling device under different conditions (during a deceleration event, during an idle period, and during an acceleration event). In each case the operation of the circuit is shown both when the rechargeable source is charging the supercapacitor and when the rechargeable source is not charging the supercapacitor. The arrows in the figure represent the direction of current flow.

Figure 13 illustrates circuit operation when the load handling device is experiencing a deceleration event. Energy is recovered from electrical load 104 (eg, from a drive mechanism or lift mechanism) and directed to ultracapacitor 102 by energy recovery circuit 112 . The rechargeable power source 100 supplies power to a non-motive electrical load 106 . Actually the circuit diagram is two separate circuits.

Figure 14 shows the operation of the circuit when the load handling device is experiencing a deceleration event and the rechargeable power supply is charging the super capacitor. Energy is recovered from electrical load 104 (eg, from a drive mechanism or lift mechanism) and directed to ultracapacitor 102 by energy recovery circuit 112 . Rechargeable power source 100 supplies power to ultracapacitor 102 and non-motive electrical load 106 . For this to work, the power rating of the super capacitor must be sufficient to receive power from the energy recovery circuit and the rechargeable power source.

Figure 15 shows the operation of the circuit when the load handling device is idle. The rechargeable power source 100 supplies power to a non-motive electrical load 106 . The source DC-DC converter 108 may be turned off such that no power is provided to the ultracapacitor 102 .

Figure 16 shows the circuit operation when the load processing unit is idle and the rechargeable power supply is charging the supercapacitor. The rechargeable power source 100 supplies power to the non-motive electrical load 106 and the ultracapacitor 102 . The load DC-DC converter 110 may be turned off such that no power is provided to the electrical load 104 . The circuit may have an active mode where the load processing device is in urgent need of acceleration, in which case the load DC-DC converter 110 may be connected in preparation for powering the electrical load 104 .

Figure 17 illustrates circuit operation when the load processing device is experiencing an acceleration event. The ultracapacitor 102 provides power to an electrical load 104 (eg, from a drive mechanism or a lift mechanism). The rechargeable power source 100 supplies power to a non-motive electrical load 106 . Actually the circuit diagram is two separate circuits.

Figure 18 Circuit operation when the load handling device is experiencing an acceleration event and the rechargeable power supply is charging the supercapacitor. The ultracapacitor 102 provides power to an electrical load 104 (eg, from a drive mechanism or a lift mechanism). The rechargeable power source 100 supplies power to a non-motive electrical load 106 . If the impedance of the electrical load 104 is lower than the impedance of the ultracapacitor 102, then the rechargeable power source 100 can supply power to the ultracapacitor 102, otherwise the rechargeable power supply can supply power to the electrical load.

The rechargeable power supply provides average current

One of the main advantages of using a supercapacitor to power a load processing device is that the supercapacitor is subjected to charge and discharge cycles rather than a rechargeable power source. Rechargeable power supplies take average current, not cycling.

Figure 19 is an illustration of the principles of use of supercapacitors. The current through the electrical load is plotted for the time for a storage container weighing up to 15 kg to be lowered to a depth of 12 grid cells in the grid storage system and then raised again. The solid line represents the current supplied to/recovered from the lift drive assembly (electrical load). The figure first shows a deceleration event in which the lift drive assembly lowers the storage container from the container receiving space of the load handling device into the storage grid, while kinetic energy is recovered from the storage container and converted into electrical energy (negative current ). Next is shown an acceleration event in which energy is provided to the lift drive assembly to lift the storage container up to the top of the storage grid and place the storage container within the container receiving space of the load handling device (positive current). If only the rechargeable power source were used to power the lift drive assembly of the load handling unit, the rechargeable power source would be subjected to transient currents as high as 23 amps (deceleration) and 14 amps (acceleration). Such surges in current, together with the transient nature of the current, include a large number of partial charge and discharge cycles, which can accelerate the aging of the rechargeable power source. This effect is even more certain if the rechargeable source is a battery.

The dashed line in Figure 19 represents the average current required by the electrical load. The average current is around 1 amp (deceleration). If a supercap placed between the rechargeable source and the electrical load acted as a perfect filter, the supercap would receive the entire current signal including all transients, while the rechargeable source would see 1 amp of average current. Removing the transient means that the rechargeable power supply does not need to undergo any charge-discharge cycles, significantly extending its life expectancy. Supercapacitors are well suited to handle transients in electrical current because they have high power density and do not age prematurely from numerous charge-discharge cycles.

The efficiency of the energy storage system is also improved using assemblies consisting of one or more supercapacitor modules. Power loss is proportional to the square of the current, so less current in a rechargeable source results in a much lower power loss. In the scenario described above and shown in Figure 19, the heat generated in the rechargeable power source during the lowering of a storage container weighing up to 15 kg to a depth of 12 grid cells and raising it was 230 J/Ohm. Using an assembly of one or more supercapacitor modules to power the lowering and raising of the storage container will reduce this heat generation in the rechargeable power supply to 2.8J/Ohm (calculated using average current). This reduces the heat generated by a factor of 82.

In addition to improving efficiency, reducing power loss is especially important when load handling units handle refrigerated or frozen merchandise in fulfillment centers and fulfillment centers need to be kept cool. The heat dissipation of the rechargeable power supply in the load handling unit means that the cooling system in the fulfillment center needs to expend more energy to maintain the required low temperature.

Supercapacitor as main power supply, rechargeable power supply as auxiliary power supply

In a specific embodiment of the present invention, the supercapacitor 102 can be used as the main power supply of the load processing device, which is supplemented by the rechargeable power supply 100 . This enables the load processing device to operate with the supercapacitor as the main power source and thus benefit from the advantages of fast charging of the supercapacitor at the supercapacitor charging station.

When the rechargeable source is a battery, the relatively long charging time of the battery can be up to several hours, representing a significant downtime during which the load handling unit will remain inactive on the grid frame structure or non-operational state. If a large number of load handling devices are operating on the grid framework to fulfill customer orders during a given period of time, one or more load handling devices remaining idle for extended periods of time can adversely affect the fulfillment center's or distribution warehouse's ability to fulfill orders in a timely manner. This is particularly the case where the load handling device is used in a logistics system that provides home delivery of merchandise to customer premises upon receipt of an order for the merchandise. In this case, the delivery information with the delivery address is used by online retailers such as Amazon and Ocado UK to deliver the goods to the customer's delivery address. To alleviate such problems, online retailers such as Ocado UK offer load handling devices that operate on grid frames for buffering to cater for load handling devices that remain idle for charging. In extreme cases, extend the time period for order fulfillment to accommodate this downtime. Using a supercapacitor as the primary power source solves the disadvantage of slow battery charging, reduces downtime, and facilitates efficient fulfillment of customer orders.

Batteries based roughly on lithium-ion, nickel-cadmium, nickel-metal hydride or lithium-ion polymer battery technology rely on chemical reactions to store electrical energy. The effectiveness of these batteries diminishes due to damage to the Li-ion cells after repeated charging, so the ability of the batteries to store charge for extended periods of time also decreases over time.

Charging stations for supercapacitors typically operate at higher currents than battery charging stations because supercapacitors have a higher power density and therefore can accept charging at higher power (which also has the advantage of fast charging). Storage grids can be equipped with two types of charging stations, one with a higher power rating/higher current for charging super capacitors and one with a lower power rating/lower current for charging Charging power supply.

The load handling device may be controlled by a control system that monitors the charge level of the energy storage system. The control system may determine whether the energy storage system of the load handling device requires charging and direct the load handling device to move to a charging station if the charge level drops below a predetermined threshold charge level. With dual power sources, the control system can determine whether a supercapacitor or rechargeable power source needs to be charged, select an appropriate charging station, and direct the load handling unit to move to the selected charging station on the storage grid.

Alternatively, a single type of combination charging station may be provided, which may be configured to provide low current (for slow charging of a rechargeable power source) or high current (for fast charging of a supercapacitor). The control system determines when the energy storage system of the load handling unit needs to be charged, determines whether the super capacitor or rechargeable power source needs to be charged, selects the appropriate combined charging station, and directs the load handling unit to move to the selected charging station on the storage grid And determine whether high charging current or low charging current should be used.

The charging station may be an inductive wireless charging station.

In the current embodiment of the invention, the pack of one or more supercapacitor modules is the main power source, so most of the charging will be a quick charge of the pack of one or more supercapacitor modules. The rechargeable power supply only needs to be recharged occasionally when the battery runs out.

Rechargeable power supply for auxiliary power after grid downtime

Sometimes the entire storage system needs to be taken offline for short periods of time (known as "grid downtime") to perform maintenance activities or to troubleshoot load handling equipment. This is where the problem arises if the load handling unit is only powered by the supercapacitor as the main power source. Supercapacitors have a high self-discharge rate. Typically, after an hour of inactivity, the supercapacitor will partially discharge below the predetermined threshold voltage for powering the electrical load. required electricity. After the grid downtime is over and the load handling device is restarted, the load handling device may not be able to return to the charging station on its own power. Before the load handling devices become operational again, they will need to be retrieved from their location and sent to a charging station, which prolongs the grid downtime period.

This problem is solved by utilizing the rechargeable power source as a backup power source when the supercapacitor as the main power source has been discharged, especially when the rechargeable power source is a battery. The battery has the advantage of a low self-discharge rate, so after a period of inactivity, the battery does not discharge significantly. After grid downtime for maintenance activities, the state of charge of the supercapacitor has dropped to a level where it cannot provide the required power, the rechargeable power source will be able to provide backup power to the electrical load to enable the load handling device to move.

The load handling device can switch to operate on power from the rechargeable power source when the supercapacitor 102 is partially or fully discharged, thereby avoiding the load handling device from being depleted and stuck on the grid and requiring the load handling device to be retrieved and sent to the grid. Downtime to the charging station becomes a necessary risk.

Supercapacitors in Low Temperature Environments

Supercapacitors outperform battery technology at low temperatures, making load-handling devices that use supercapacitors as their primary power source particularly suited for these operating environments.

Load handling units may operate in fulfillment centers kept at low temperatures, for example, when fulfilling customer orders for refrigerated or frozen goods. Not only does the release of heat from the energy storage system of the load handling unit represent a waste of energy, but more energy must be expended to keep the fulfillment center cool.

Table 2 shows the performance of the Li-ion battery powering the load handling device on the grid frame structure.

Table 2: Battery performance of Li-ion batteries in load handling units.

Typically, lithium-ion batteries need to be charged for 15 minutes for every 4 hours of discharge. During the 4 hours of operation on the grid frame structure, the power of the electrical load reached a peak value of 600W, and it was 96W at idle, because the communication device was between the controller (control unit) in the load processing device and the central control system. The communication between them consumes power. The average power consumed by the electrical load was 400W consumed throughout the 4 hour period, corresponding to an energy consumption of 100Wh per operating cycle. The energy storage system on the load handling device will need to store at least 100Wh of energy when fully charged. Lithium-ion batteries last 3 years at ambient control temperatures (10°C - 30°C) and 0.5 years at refrigerated temperatures (0.5°C).

Unlike lithium-ion batteries, supercapacitors do not suffer from the shortened lifespan of low-temperature operation. Supercapacitors are typically rated to operate down to -40°C without any degradation in performance.

Load handling units may need to operate at low temperatures when the storage system is used for refrigerated or frozen commodities. Specifically, the storage system may be located in a fulfillment center with a refrigerated or frozen environment, and the load handling unit will need to be able to operate in this environment. Freezing temperatures encompass the range of approximately -25°C to approximately 0°C, while refrigerated temperatures encompass the range of approximately -0°C to approximately 4°C. Therefore, supercapacitors are usually at their rated operating temperature in a refrigerated or freezing temperature environment.

Table 3 shows, as an example, the calculated charging current applied to a commercially available supercapacitor module with an initial charging capacity of 100 Wh at 48 volts at different desired charging and discharging times. The average power consumption over a 4 hour period for the Li-ion battery shown in Table 2 is considered to be 400W. The charging times shown in the tables for supercapacitors (from 5 seconds to 30 seconds) are much faster than for lithium-ion batteries (typically 15 minutes).

Table 4 shows the equivalent energy and equivalent discharge depth used by supercapacitors for different discharge times under the assumption that the initial charge is 100Wh. The average power consumed by the Li-ion battery in the load handling device shown in Table 2 is 400W. To draw the same power from a supercap initially charged to provide 100Wh of energy, the supercap would need to be fully discharged every 15 minutes to 100% depth of discharge. Likewise, a discharge time of 5 minutes represents a depth of discharge of 33%, which equates to an energy of 33Wh.

Based on the operation of the load processing device on the grid frame structure and the resulting power consumed by the load processing device to perform tasks on the grid frame structure, short bursts of energy can be sent to the grid frame structure by accessing one or more super capacitor charging stations to the supercapacitor module to supplement the supercapacitor module with sufficient power for the load processing device to complete its operation. The charging time of the supercapacitor modules is only a fraction of this time compared to the time it takes to perform a task on a grid frame structure. Because the charging time is relatively short (in seconds) and because the supercapacitor can tolerate multiple charging cycles, the load handling device can visit the charging station multiple times during operation on the grid frame structure. For example, a supercapacitor can cycle more than 290,000 times at 100% depth of discharge, which is equivalent to a working life of about 8 years, which is much longer than that of ordinary batteries.

Table 3: Charge current for different charge and discharge times at 48 volts

Table 4: Energy used (Wh) at an average power consumption of 400W.

Allocation of supercapacitor modules to lower the center of mass of the load handling unit

In a specific embodiment of the present invention, the load handling device only occupies one grid space or grid unit of the grid frame structure (as shown in Fig. 4 and Fig. 5). This has the advantage that a greater number of load handling devices can be active on the grid at any given time. However, the load handling apparatus shown in FIG. 5 with the container receiving recess 40 in the lower portion would have the lift drive assembly, drive mechanism and energy storage system located above the container receiving recess. A disadvantage of this arrangement is that the center of mass of the load handling device can be high, which has a negative effect on the stability of the load handling device.

To lower the center of mass and thereby improve the stability of the load handling device, one or more supercapacitor modules may be distributed around the outside of the container receiving recess. FIG. 20 illustrates the load handling device 30 including a container receiving recess 40 within the carrier body 32 . The carrier body 32 includes four outer walls 42 on four sides of the load handling device 30 and four inner walls 44 constituting the inner surface of the carrier body, and the container receiving recess 40 is located therein. A gap 46 exists between the inner wall 44 and the outer wall 42 of the carrier body.

FIG. 21 shows how a supercapacitor module 48 is arranged in the gap 46 between the inner wall 44 and the outer wall 42 . It should be appreciated that the center of mass of the load handling device will be lowered due to the placement of the ultracapacitor module 48 at a lower position in the load handling device. Absent such an arrangement, the assembly of one or more ultracapacitor modules would otherwise be placed in the upper portion of the load handling device, above the container receiving recess 40 . The lower center of mass makes the load handling unit more stable.

Stability of load handling devices is an important consideration. An unstable load handling device may be at risk of toppling over, necessitating grid downtime to retrieve the load handling device and return it to an upright position.

Recalibration of battery state-of-charge calculations with periods of low current consumption

Figure 22 shows the charge and discharge curves of a Li-Ion battery in a load handling unit, plotting the battery state of charge (SOC) against the battery voltage. Data was measured after the load handler had been operating on the grid for one day. Three sets of data are plotted: i) SOC obtained by measuring cell voltage at a batch of different cell current values, ii) open circuit voltage curves from the cell manufacturer's datasheet, iii) The estimated SOC of the battery fuel gauge. Since i) and iii) are measured under a batch of different battery current values, there are several sets of data instead of only one line. The data points for ii) are at a single current (open circuit voltage corresponds to zero current), so there is only one data line. From Figure 22 it can be seen that the three data sets are all aligned; i) the SOC obtained by measuring the voltage and iii) the estimated SOC from the battery fuel gauge aligns with the manufacturer's data point grouping is done at zero current Determination. This alignment indicates that the battery fuel gauge accurately measures the true SOC of the battery.

The estimated SOC of the battery fuel gauge is based on the coulomb counting method. This method measures the current drawn from and supplied to the battery and integrates it with time to estimate the remaining usable charge. Coulomb counting has the advantage of being simple and straightforward to implement, but because amperometric measurements cannot be perfectly accurate, the method is subject to drift over time if the measurements are not recalibrated to a standard point .

Figure 23 shows the charge and discharge curves of a Li-ion battery in a load handling device, plotting (SOC) against the battery voltage in a similar manner to Figure 23. Data were measured after the load handler had been running continuously on the grid for several days. Three sets of data are again plotted: i) SOC obtained by measuring cell voltage at a batch of different values of cell current, ii) open circuit voltage curve from the cell manufacturer's data sheet, iii) a batch of different values of cell current Estimated SOC of the battery fuel gauge below. From Figure 23 it can be seen that the SOC obtained by measuring the voltage is still aligned with the manufacturer's data along the charging curve. However, this is not the case for the estimated SOC from the battery fuel gauge, which does not line up with the manufacturer's data. There is a gap indicated by the arrows in Figure 23 between the battery fuel gauge SOC reading and the actual SOC. This gap is as high as 15-20% of the SOC size, and indicates that the battery fuel gauge is no longer accurately reporting the true SOC of the battery, but in fact overestimates the available SOC. This is true for both charge and discharge curves.

This inaccuracy in the battery fuel gauge's estimated SOC is a problem because SOC is used by the control system to decide when to recharge the battery. For example, the control system may require the load handling device to travel to a charging station when the SOC has dropped below 30%. When the battery fuel gauge indicates that the SOC has dropped below 30%, the true SOC may be as low as 10%-15%. This can be a problem because it increases the risk of the load handling unit running out of battery power before it reaches the charging station. In this case, it may be necessary to stop the operation of the grid while the load handling unit is retrieved and sent to the charging station.

This inaccuracy in the estimated SOC of the battery fuel gauge gradually increases with operating time. After one day of operation on the grid, the battery fuel gauge accurately reported the SOC (see Figure 22), but after several days of continuous operation on the grid, the battery fuel gauge no longer accurately reported the SOC.

The problem here is that battery capacity is easily underestimated due to inaccuracies in tracking current transient peaks. If current transients occur at a higher frequency than the battery fuel gauge is measuring current, then the peaks will not be captured accurately. Underestimating the current supplied by the battery results in an overestimation of the available charge remaining in the battery, which explains why the estimated SOC from the battery fuel gauge drifts upwards over time. Underestimating the current supplied by the battery, even by a small amount, can accumulate over time and cause a drift between the battery fuel gauge's estimated SOC and actual SOC.

This problem can be solved by recalibrating the battery fuel gauge by allowing the battery cell to go through periods of low current drain where the battery draws zero or as little current as possible. This rest period gives the battery fuel gauge an opportunity to recalibrate the estimated SOC and will tend to reduce the 'offset'.

Recalibration can be accomplished by checking that the battery fuel gauge's estimated SOC at a known voltage and current matches the expected SOC at the same voltage and current from the manufacturer's data sheet. This can be any known current, but zero current is convenient since open circuit voltage curves are readily available from battery manufacturers. The expected SOC can be read from the manufacturer's OCV curve for a given voltage when the battery current is zero. The battery fuel gauge may thus recognize that the expected SOC is different from the battery fuel gauge's estimated SOC and recalibrate by updating the battery fuel gauge estimated SOC to match the expected SOC.

Another way to estimate SOC is voltage measurement instead of coulomb counting. But because the battery voltage drops sharply over time due to battery discharge, a small change in voltage also corresponds to a large change in SOC. This means that voltage-based SOC estimates are not always accurate. Coulomb counting is a better method of estimating SOC than measuring voltage, assuming the calibration problem can be resolved.

A load processing device having an energy storage system comprising an assembly of one or more supercapacitor modules and a battery can make better use of dual power sources by using supercapacitors for only a short period of time. This allows the battery to have low current drain periods of zero current or low current demand at the end, during which the battery fuel gauge can recalibrate and thus display a more accurate SOC measurement.

While zero current draw is ideal for periods of low current draw in order to recalibrate the battery fuel gauge to the manufacturer's open circuit voltage curve, it may not be possible to achieve zero current draw in practice, so the current draw should be kept as low as possible. Low. Periods of low current consumption may be achieved by the controller periodically disconnecting the battery from the assembly of one or more supercapacitor modules so that no power is supplied to the supercapacitor. "Periodic disconnection" means disconnection for a short period of time (for example, once every four hours) after a predetermined period of time has elapsed.

Battery SOC balance

The individual cells in a battery pack naturally have somewhat different capacities and therefore may be in different states of charge during a charge-discharge cycle. Variations in capacity may be due to manufacturing variances, assembly variances (e.g. cells from one manufacturing batch are mixed with others), cell aging, impurities, or environmental exposure (e.g. some cells may be exposed to heat from nearby heat sources such as motors, electronics, etc. additional heat) and can be exacerbated by the cumulative effect of additional loads such as battery monitoring circuits often found in battery management systems.

A battery may include a plurality of battery cells connected in series. In this case, the cells must be "balanced" by maintaining as much as possible the same voltage/SOC in each cell. Balancing the components that make up a battery cell helps maximize energy capacity and improves battery life.

A battery management system is used to monitor the condition of the battery pack, including individual cell properties such as temperature and voltage. When charging, the entire battery pack can be charged until only one (battery) cell reaches its maximum safe charging voltage, even though the other cells still have capacity for further charging. Therefore, the battery cell with the lowest voltage limits the charging voltage of the entire battery pack. Likewise, a battery pack can only be safely discharged until one (battery) cell is fully discharged, even if the other cells still have charge available. Therefore, the cell with the lowest charge capacity limits the charge capacity of the entire battery pack. Failure to stop charging/discharging when a (battery) cell has reached its upper limit may permanently damage the cell. Lithium-ion batteries are particularly susceptible to chemical damage from excessive voltage or current.

Cell balancing redistributes energy from cells with higher energy capacity to cells with lower energy capacity. Battery balancing can be passive balancing, where energy is drawn from the most charged (battery) cells and dissipated as heat, or active balancing, where energy is drawn from the most charged (battery) cells and is transferred to the least charged (battery) unit. Active cell balancing can be done through a DC-DC converter.

A load processing device having an energy storage system comprising an assembly of one or more supercapacitor modules and a battery may draw a constant low current from the battery below a predetermined threshold current by utilizing the supercapacitor to meet the acceleration needs of the load processing device. to take advantage of dual power supplies. A constant low current below a predetermined threshold current provides optimal conditions for cell balancing. The optimal predetermined threshold current will depend on the size and specifications of the battery and can be determined by the battery manufacturer. For example, the predetermined threshold current may be a current lower than 3 amperes.

Opportunistically charge supercapacitors at grid locations above access points

To fulfill a customer order, the load handling device may retrieve the storage container and transport it to a grid location on the storage grid above the access point. The storage container is then lowered down the chute to an access point where it can then be accessed to fulfill the order. An operator may remove items from storage containers at the access point and package them as part of the customer's order. The load handling device may then lift the storage container through the grid and into the container receiving space before repositioning the storage container in place within the storage grid.

The grid locations on the storage grid above the access points are ideal locations for charging assemblies consisting of one or more supercapacitor modules because load handling devices frequently travel to these locations to deliver storage containers to the access points . Accordingly, the storage system may include one or more supercapacitor charging stations located at grid locations above the access points.

Preferably, the supercapacitor charging station can be a high-rate inductive supercapacitor charging station, so that the charging of the supercapacitor during the raising and lowering operation can be completed by high-rate inductive charging. This allows the super capacitor to be fully charged in a short time (in seconds). Since the supercapacitor charges very quickly, it can be done in the time the load handling device spends at the grid location when lowering and raising the storage container. Grid locations above the access points are frequently accessed by the load handler, so these accesses are sufficient to satisfy all supercapacitor charging requirements. The load handling device does not need to separately visit other charging stations to charge an assembly consisting of one or more supercapacitor modules. Therefore, the charging of the supercapacitor can be completed during the normal operation of the load processing device without additional time.

After the supercapacitor has been fully charged at a grid location on the storage grid above the access point during the raising or lowering operation, the supercapacitor can be used to charge the rechargeable power source. This can be achieved by a controller on the load processing device instructing the assembly of one or more supercapacitor modules to charge the rechargeable power source. Alternatively, if the load handling device is going to a grid location for a lift or lower operation, the supercapacitor can be used to charge the rechargeable power source in advance, so that the supercapacitor is partially discharged and ready to be charged by the supercapacitor charging station.

Supercapacitors can be used to charge rechargeable sources at low currents. As mentioned above, if the rechargeable source is a battery, subjecting the battery to a low constant current below a predetermined threshold current helps balance the cells to ensure a uniform state of charge among the different cells, which can extend the life of the battery. Current can be limited to allow cell balancing. The controller may instruct the ultracapacitor to charge the rechargeable power source at a current below a predetermined threshold current.

The rechargeable power source may only need to be charged by the supercapacitor if the supercapacitor is charged frequently enough at a high enough charge rate. This eliminates the need to provide a separate charging station on the storage grid to charge the rechargeable power source. The load handling device also no longer needs to travel to a rechargeable power source charging station on the storage grid and spend time there while the rechargeable power source is charging. This would effectively eliminate the need for downtime to charge the load processing devices, allowing the load processing devices to continue to operate on the storage grid.

As noted above, the load handling device may be controlled by a control system that monitors the charge level of the rechargeable power source and instructs the load handling device to proceed to a charging station if the charge level drops below a predetermined threshold charge level. In this embodiment of the invention, the load processing device can operate continuously on the storage grid without access to the rechargeable power source charging station, the supercapacitor charging station enables the load processing device to maintain the voltage level of the rechargeable power source for Above a predetermined threshold voltage for powering an electrical load.

The recalibration of the estimated battery state of charge as described above is particularly important where the load processing device operates continuously on the storage grid.

Battery/Super Cap Technology

It should be understood that components composed of one or more supercapacitor modules may include, but are not limited to, capacitors, supercapacitors, supercapacitors, lithium capacitors, electrochemical double layer capacitors, electric double layer capacitors, pseudocapacitors, hybrid capacitors, or these capacitors Certain combinations of technologies.

It should be understood that rechargeable power sources may include, but are not limited to, lithium ion batteries, lithium ion polymer batteries, lithium air batteries, lithium iron batteries, lithium iron phosphate batteries, lead acid batteries, nickel cadmium batteries, nickel metal hydride batteries, nickel zinc batteries , sodium-ion batteries, sodium-air batteries, thin-film batteries, solid-state batteries, or smart batteries carbon foam-based lead-acid batteries, or some combination of these technologies.

Advantages of Using a Low Pass Filter

A low pass filter is beneficial to reduce the number of transient current loops in the rechargeable power supply. High-frequency transients in the current supplied to the electrical load are "cancelled" by the low-pass filter circuit, so that the high-frequency transient components of the current through the rechargeable power source are removed. This keeps the rechargeable power supply immune to surges in current draw. This is particularly advantageous where the rechargeable source is a battery, since reducing transients in current has been shown to reduce the aging effects of the battery.

Removing the transient means that the rechargeable power supply is no longer subject to any charge-discharge cycles, significantly extending its life expectancy. Supercapacitors are well suited to handle transients in electrical current because they have a high power density and do not age prematurely from numerous charge-discharge cycles.

Using a low pass filter also improves the efficiency of the rechargeable power supply. Power loss is proportional to the square of the current, so lower currents result in significantly lower power losses.

In addition to improving efficiency, reducing power loss is especially important when load handling units are handling refrigerated or frozen merchandise and fulfillment centers need to be kept cool. The heat dissipation of the rechargeable power supply in the load handling unit means that the cooling system in the fulfillment center needs to expend more energy to keep it at the required low temperature.

Circuit diagram with low pass filter highlighted

FIG. 24 is a circuit diagram showing rechargeable power source 100 connected in parallel with electrical load 104 and filter circuit 116 . Electrical load 104 includes one or more motors that may include one or more motors that move the vehicle on rails in the X and Y directions, respectively, through sets of drive wheels 34 and 36, and/or drive a lifting device or lifting mechanism to lift the storage container from above. One or more engines.

For ease of illustration, the circuit diagram of FIG. 24 shows rechargeable power source 100 as a single battery cell and electrical load 104 as a single electrical load. It should be understood that the rechargeable power source of the load processing device is not limited to batteries, and that batteries may include assemblies of one or more battery cells, not just a single battery cell, and that electrical loads may include a number of motors and other components, rather than a single electrical load.

DC-DC Converter

The circuit may additionally include one or more DC-DC converters. As shown in FIG. 25 , the circuit may additionally include a filtered DC-DC converter 118 between the electrical load 104 and the filter circuit 116 . The function of the filtering DC-DC converter 118 is to convert the voltage at both ends of the rechargeable power source into different voltages at both ends of the filtering circuit. With a filtered DC-DC converter 118 for the filter circuit 116, the voltage across the chargeable source can be the same as the load voltage.

The filtered DC-DC converter 118 between the electrical load 104 and the filter circuit 116 includes a step-up converter or a step-down converter. A buck converter is particularly advantageous if the filter circuit includes one or more supercapacitors connected in parallel with the electrical load 104, since the voltage across the one or more supercapacitors will be lower. Lower voltages mean lower power rated supercapacitors or fewer parallel connected supercapacitors are required.

The circuit may additionally include a source DC-DC converter 108 between the rechargeable power source 100 and the filter circuit 116 as shown in FIG. 26 . The function of the source DC-DC converter 108 is to convert the voltage across the rechargeable power source 100 into different voltages across the filter circuit 116 . It should be understood that with the two DC-DC converters 108 and 116, the rechargeable power source 100 and the electrical load 104 may be at the same voltage or at different voltages.

The source DC-DC converter 108 between the rechargeable power source 100 and the filter circuit 116 may comprise a step-up converter or a step-down converter.

low pass filter

A low pass filter has a cutoff frequency; and signals with frequencies below the cutoff frequency are allowed to pass through the filter and signals with frequencies above the cutoff frequency are cut off. The filter attenuates high frequencies in the input signal, but signals below the cutoff frequency receive little attenuation.

An ideal low pass filter will allow frequencies below the cutoff frequency to pass through the filter unchanged while completely eliminating all frequencies above the cutoff frequency. The frequency response is a step function. In practice, electronic low-pass filters are not ideal filters, and the exact frequency response of the filter depends on the filter design.

Active and Passive Filters

Filtering circuits can be active or passive. Active filters require additional power and include amplification to increase signal strength. Gain is greater than integral, increasing the power available in the signal compared to the input. Passive filters contain no amplification to boost the signal and require no additional power supply. Passive filters cannot have net power gain and dissipate energy from the signal, which makes the gain less than integral and the output signal's amplitude less than its corresponding input signal.

Passive filter circuits can be constructed from components such as resistors, inductors and capacitors. The advantage of not needing an additional power supply is that it makes the circuit less complex.

The advantage of active filters is that they can achieve a given transfer function over some frequency range without the use of inductors, which are relatively large and costly components compared to resistors and capacitors. Since no inductor is used, active filters can be made with very compact dimensions and do not generate or interact with magnetic fields that may exist.

multi-order filter

Multi-order filters can be built by "stacking" filter circuits together. Higher order filters have a greater attenuation of the signal as the frequency increases above the cutoff frequency. As the order of the filter increases, the filter approaches the characteristics and behavior of an ideal filter.

Multistage active filters have the advantage that the stages are well isolated from each other, so their characteristics are independent of source and load impedances. In contrast, multi-order passive filters are more difficult to design because each order must consider the frequency-dependent loading of the previous order.

Filter Circuit Embodiment

One method of filtering signals is an RC filter, a circuit that includes one or more resistors and one or more capacitors driven by a voltage or current source. The circuit is named "RC" because R and C are common symbols for resistance and capacitance, respectively. A first order RC circuit is the simplest type of RC circuit and includes a resistor and a capacitor. An RC circuit for filtering current signals consists of a resistor and capacitor driven in parallel by a current source. The cutoff frequency is determined by the RC time constant of the circuit. Figure 27a shows a parallel RC circuit. A first order RC filter can be constructed using a supercapacitor in parallel with the rechargeable power source 100 and in parallel with the electrical load 104 .

Another way to filter signals is the RL filter, which is a circuit that includes one or more resistors and one or more inductors driven by a voltage or current source. The circuit is named "RL" because R and L are common symbols for resistance and inductance, respectively. A first order RL circuit is the simplest type of RL circuit and includes a resistor and an inductor. An RL circuit for filtering a current signal consists of a resistor and an inductor driven in parallel by a current source. Figure 27b shows a parallel RL circuit.

Another alternative is an RLC filter, which is a circuit that includes one or more resistors, one or more inductors, and one or more capacitors. A second-order RLC circuit is the simplest type of RLC circuit and consists of a resistor, an inductor, and a capacitor connected in series or parallel. The circuit is named "RLC" because R, L, and C are common symbols for resistance, inductance, and capacitance, respectively. Uses of RLC circuits include as low-pass filters, among other applications. RLC filters are described as second order filters because the voltage or current in the circuit can be described by second order differential equations. Figure 27c shows a simple RLC circuit.

Higher order passive RLC filters such as Butterworth filters can also be used (Fig. 27d).

The above circuits are all passive filters. Active low-pass filtering circuits can be constructed, for example, by using operational amplifiers. Figure 27e shows an active filter circuit with an operational amplifier.

An operational amplifier is characterized by a gain-bandwidth product (GBWP), which is the product of the bandwidth of the amplifier and the gain at the measured bandwidth. The gain-bandwidth product is nearly independent of the gain at which it is measured, so the gain, to a first approximation, is inversely proportional to frequency. As an example, Figure 28 shows an op amp with a GBWP of 1MHz. The operational amplifier has a gain of 1 (0dB) at 1MHz, a gain of 10 (20dB) at 100kHz, and a gain of 1000 (60dB) at 1kHz. The DC gain for this example is 100000, or 100dB. This inverse proportional response coupled with high DC gain gives the op amp the characteristics of a first-order low-pass filter. The cutoff frequency is obtained by dividing GBWP by the DC gain. For the op amp shown in Figure 27c, the GBWP is 1MHz and the DC gain is 100000, so the cutoff frequency is 10Hz. Signals at frequencies 10Hz and below are allowed to pass with maximum gain, while higher frequency signals have lower gain.

Boost/reduce transient current during operation

Figure 19 shows the transient nature of the current flow of the load handling device on the storage grid during step-down and step-up operations.

Figure 29 illustrates another embodiment of the hoisting operation of the load handling device. First, the gripper 39 is lowered into the storage grid (deceleration event) to a depth of 21 grid positions. The gripper device then grabs the storage container 10 with a mass of 30 kg and lifts the storage container up to the top of the grid and into the container receiving space within the load handling device (acceleration event). The gripper then lowers the storage container back down to its original position on the storage grid (second deceleration event), releases the storage container, and lifts the gripper back up to the top of the grid (second acceleration event). From Figure 29 it can be seen that the first acceleration event in which the gripper was lifted with a 30 kg storage container had a much higher average current than the second acceleration event in which the gripper was lifted without a load. Also, the second deceleration event which was lowered when the gripper was loaded with a 30 kg storage container had a much higher average current than the first acceleration event which was lowered when the gripper was not carrying a load.

Table 5 below lists the average current of each of the four acceleration and deceleration events shown in FIG. 29 , and the peak-to-peak variation of the current in this event. It can be seen that the variation is significant, with a peak-to-peak variation of over 40 amps for the first acceleration event.

Table 5: Average current and current peak-to-peak variation during lifting and lowering operations.

Fourier transform of current signal

To better understand the high frequency components of the current signal, Figures 30a-d plot the Fourier transform of the current signal plotted in Figure 29 . The sampling frequency is 6250Hz, so the Fourier plot ranges from zero to the Nyquist frequency of 3125Hz. Figure 30a plots the entire Fourier transform showing large spikes at low frequencies and a number of small spikes in the frequency range up to 1000 Hz. (Overprinted) Figure 30b plots the same Fourier transform in the range 0-1000 Hz and with amplitudes up to 1, from which it can be seen that most of the small impulses occur at frequencies above 20 Hz. Figure 30c plots the same Fourier transform over the range 0-20 Hz and up to 1 in amplitude. It can be seen that the low frequency peak is below 1Hz, there is a large peak around 9Hz, and a second around 11Hz. Figure 30d plots the Fourier transform in the 0-1 Hz range; although the exact shape of the spectrum is more difficult to see at this resolution, a peak around 0.08 Hz can be seen. 0.08Hz corresponds to a cycle of about 12.5 seconds, which is a cycle of lifting and lowering operations (from Figure 29 it can be seen that the time between the start of the first deceleration event and the start of the second deceleration event is about 12.5 seconds, and The time between the start of the first acceleration event and the start of the second acceleration event was about 12.5 seconds).

By looking at the Fourier transform of the current signal, it can be seen that most of the noise in the current is between 20hz and 1000Hz, with additional impulses at 9Hz and 11Hz. A 20Hz or 7Hz low pass filter will remove most of these transients and produce a smoother signal.

The above embodiment demonstrates how to determine the predetermined cut-off frequency through the Fourier transform of the signal. When the predetermined cutoff frequency is known, the filter circuit can be designed to act as a low pass filter and pass frequencies below the predetermined cutoff frequency and cut frequencies above the predetermined cutoff frequency.

For passive low-pass filter circuits, the dimensions of the components may be chosen such that the circuit frequency is equal to a predetermined cutoff frequency. For example, in an RC filter circuit, the resistor and capacitor values can be chosen such that the circuit frequency is the desired cutoff frequency. In the RL filter circuit, the resistance and inductance values can be selected such that the circuit frequency is a predetermined cutoff frequency. In an RLC filter circuit, the resistance, inductance and capacitance values can be selected so that the circuit frequency is a predetermined cutoff frequency.

For an active low-pass filter circuit using an operational amplifier, the characteristics of the operational amplifier can be chosen such that the cutoff frequency of the circuit is the same as the predetermined cutoff frequency. As described above in connection with Figure 28, to a first approximation the cutoff frequency of an op amp can be calculated by dividing its GBWP by its DC gain.

Low Pass Filter RC Circuit

The principles of designing a low-pass filter circuit with a predetermined cut-off frequency will be shown in conjunction with a first-order RC filter. It should be understood that this particular circuit is one of many possible implementations of the filter design and is not intended to be limiting.

Figure 27a is a diagram showing a simple first order RC filter circuit with resistors and capacitors connected in parallel. The time constant of the filter is calculated from the product of the resistor and the capacitor, so the cutoff frequency f is given by Equation 1 below:

等式 1

Equation 1

where R is the resistance of the circuit and C is the capacitance of the circuit.

Reactance X is given by Equation 2. At higher frequencies, the reactance decreases and the capacitor effectively acts as a short circuit:

等式 2。

Equation 2.

The low frequency components of the current signal are attenuated by the reactance of the capacitor; instead of flowing freely through the capacitor, the current accumulates on the capacitor plates. Pure DC current (the zero-frequency component of the current signal) will not pass through the capacitor at all, so the resistor must be replaced. Low frequency components will not be completely blocked by the capacitor, but their amplitude will be clipped and at least part of the current directed through the resistor.

The high frequency component of the current signal passes through the capacitor very smoothly because the capacitor has little time to accumulate charge before the high frequency component of the current changes direction. Current preferentially flows through capacitors over resistors, effectively shortening the circuit.

In practice, capacitors operate between these two extremes because the current signal includes components over a range of frequencies.

For the current signal described above and shown in Figure 29, looking at the Fourier transform of the current signal (shown in Figure 30) shows that a predetermined cutoff frequency of around 20 Hz or (preferably) around 7 Hz is suitable. Equation 1 can be used to select the appropriate R and C values to create a filter circuit with a circuit frequency of 20Hz or 7Hz.

Equation 1 can be reformulated to calculate the required capacitance (Equation 3):

等式 3。

Equation 3.

Using a resistor with a resistance of 3.5 mΩ, using Equation 3 gives the required capacitance of 2.3F for the 20Hz circuit and 6.6F for the 7Hz circuit.

Demonstration of low-pass filtering by simulation

Figure 31 is a Simulink model of a simple RC filter circuit with resistors and capacitors in parallel. The 48V voltage source represents the rechargeable power source and the capacitor represents the electrical load. The resistance of the resistor is 3.5 mΩ. The current signal of FIG. 29 is applied across a resistor and the current signal in a rechargeable power supply is plotted.

Figure 32 plots the current signal through the resistor and through the rechargeable power supply. As calculated above, a filter circuit with a circuit frequency of 20 Hz should filter out most of the transients from the current signal. Figure 32a is the raw current signal, the same as in Figure 29. Figure 32b is the filtered signal at the rechargeable power source with an RC filter circuit with a circuit frequency of 20 Hz, a resistor resistance of 3.5 mΩ, and a capacitor capacitance of 2.3 Farad. It can be seen that the transients in the current through the rechargeable power source have been significantly reduced compared to the input current. The input current surge of 47 amps at the beginning of the first acceleration event around 6.5 seconds can be seen to have reduced to a significantly lower 33 amps at the rechargeable source. This proves that the use of capacitors in the filter circuit will reduce transients and surges in the current flow and thus reduce the aging effect on the rechargeable power supply.

As calculated above, a filter circuit with a circuit frequency of 7 Hz should filter out transients from the current signal as well as a 20 Hz circuit, and also filter out the peaks observed at 9 Hz and 11 Hz. Figure 32c is the filtered signal at the rechargeable power source with an RC filter circuit with a circuit frequency of 7 Hz, a resistor resistance of 3.5 mΩ, and a capacitor capacitance of 6.6 Farad. It can be seen that the transient state in the current passing through the rechargeable power supply has been significantly reduced compared with the input current, and the frequency of the 7Hz filter circuit is even reduced more than that of the 20Hz filter circuit. The input current has a surge of 47 amps at the beginning of the first acceleration event around 6.5 seconds, which can be seen to decrease to 26 amps at the rechargeable source. This impulse is modest compared to the average current of 24 amps for the first acceleration event.

Table 6 below lists the average current for each of the four acceleration and deceleration events, the peak-to-peak current variation in the event, and the filtered peak-to-peak current variation at 20 Hz and 7 Hz. It can be seen that the peak-to-peak variation is greatly reduced by filtering.

Table 6: Average current and current peak-to-peak variation during lifting and lowering operations after filtering at 20Hz and 7Hz.

Figure 33a compares the load current to the current through a rechargeable power supply with a 20Hz filter circuit, while Figure 33b compares the load current to the current through a rechargeable power supply with a 7Hz filter circuit. From these plots it is easy to see how the transients in the current signal are significantly reduced.

Non-Linearity of Lithium-Ion Batteries

Figure 34 shows a typical discharge curve for a Li-ion battery, plotting the (battery) cell voltage against the discharge capacity. Discharge is defined as 100% minus state of charge: a state of charge of 100% corresponds to a state of charge of 0% and a state of charge of 0% corresponds to a state of charge of 100%. It can be seen that the discharge curve is highly nonlinear. This means that in practice Li-ion (battery) cells do not operate over the entire voltage range. Although the voltage range of a single Li-ion cell can go up to 4.2V, in practice the highly nonlinear shape of the curve means that the cell spends most of the time between 3 and 4 volts. The graph shows only a symbolic voltage curve; in practice, the shape of the curve depends on many factors such as temperature and discharge rate. Other battery chemistries have different maximum voltages and different discharge curves, but are also non-linear. This can be a problem for load handling devices where the rechargeable source is a battery, since the load handling device cannot utilize the full range of the battery.

To power one or more load motors, several Li-ion battery cells may be arranged in series. As an example, 12 Li-ion battery cells in series provide a voltage range of up to 12 * 4.2 = 50.4V, enough to power one or more load motors at a nominal voltage of 48V. Lithium-ion (battery) cells will operate between 36V (12 x 3V) and 48V (12 x 4V) most of the time. In practice, lithium-ion batteries utilize only a fraction of their full voltage range (and thus only a fraction of their total energy storage).

Even so, in practice, once the voltage of the Li-ion battery pack drops below the threshold voltage used to power the electrical load, the load motor will not have enough power to provide the required acceleration to the load handling device. This can happen before the Li-ion (battery) cell is fully discharged, meaning that only a portion of the Li-ion (battery) cell's effective range is used for power. Once the threshold voltage is reached, the battery will not be able to provide enough power, so the load handling device must be charged. For a load handling device with a 48V Li-ion battery pack and a 48V electrical load, this threshold voltage is around 42.6V.

In some embodiments, a load handling device may need to achieve a predetermined acceleration in order to perform its function. To achieve the item throughput of a storage system that fulfills orders and meets demand, load handling devices must operate at the maximum possible acceleration on the grid. The greater the acceleration of the load handling device operating on the grid, the faster the load handling device can reach the desired grid cell when retrieving or storing storage containers from a given stack. Conversely, the less the acceleration of the load handling device operating on the grid, the longer it takes the load handling device to reach the desired grid cell and thus the more time it takes to retrieve a storage container from a given stack. As a result, in order to maintain the item throughput of the storage system and thus meet the demand for lower acceleration, a greater number of load processing devices will be required to operate on the grid.

The storage system includes a control system that manages the movement of load handling devices on the grid. A control system tracks the location of each load handler, instructs the load handler to move to a new location, and avoids collisions. If the load handling unit cannot achieve the desired acceleration, it may not be able to achieve the desired movement in the expected time. Other load handling devices may need to slow down or make detours to avoid a collision. Besides making the control much more complicated, this may slow down or disturb the paths of other load handlers on the grid, not just the under-accelerated load handlers.

Therefore, in some embodiments it may be beneficial to define a predetermined acceleration for the load handling device to perform its function. It may be a linear acceleration of the movement of the load handling device along rails on the grid frame structure, or an acceleration of the gripper device lifting the container up from the storage system into the container receiving space of the load handling device, or both. The predetermined acceleration defines the torque demand of the lift drive assembly and/or drive mechanism and thus defines the torque demand of the engine. The torque requirement defines a threshold voltage. This voltage will be called the predetermined threshold voltage, since the value of this voltage is defined by the predetermined acceleration. This is often referred to as the operating voltage of the electrical load. When the engine voltage drops below the predetermined threshold voltage, the load handling device will not be able to achieve a predetermined acceleration. In an exemplary embodiment, for a load processing device having a 48V Li-ion battery pack and a 48V electrical load, the predetermined threshold voltage is around 42.6V.

The usable part of the battery voltage range is thus further reduced. For example, a 5kWh Li-ion battery may only use the first ~1.5kWh (first third) of its energy capacity. This is a problem because the cost and mass of the battery is enormous, but only a fraction of the battery capacity is available, so the battery must be charged more often than is actually necessary. Charging requires downtime as well as time and energy spent by load handling devices traveling to and from charging stations on the storage grid.

The problem to be solved is how to make the load handling device run longer before needing to recharge the rechargeable power source.

One way to increase the time between charges is to increase the voltage of the rechargeable power source. But this is sub-optimal because high voltages require more safety measures to protect human operators. Higher voltages require components with higher power ratings and associated higher costs. Also, increasing the voltage won't solve the problem of a rechargeable power supply only operating over a portion of its effective range.

Another approach is to use a higher proportion of the operating voltage of the rechargeable source by using a second source as a "booster" so that the energy storage system can operate after the rechargeable source's voltage has dropped to a predetermined level for powering the electrical load. Sufficient power is provided below the threshold voltage.

A supercapacitor can be placed in parallel with the rechargeable power supply, which allows both the supercapacitor and the rechargeable power supply to supply the electrical load at the same voltage. But this is not ideal because it only utilizes a portion of the supercap's effective voltage range. The cost per unit energy storage of a supercapacitor is higher than that of a rechargeable power supply, and several supercapacitor modules in series may be required to achieve the required voltage.

Figure 35 compares typical discharge curves for batteries and supercapacitors. The discharge curve of a supercapacitor is approximately a straight line, with the voltage decreasing linearly with the amount of discharge (discharge is defined as 100%-state of charge). The battery discharge curve is much flatter, so for the same change in voltage, the battery will experience a greater change in state of charge. When a battery and a supercap are connected in parallel, they will see the same voltage. The difference in the shape of the discharge curve means that when a battery and supercap are subjected to the same voltage drop in parallel, the state of charge of the battery will drop more than the state of charge of the supercap, because the discharge curve of the battery is smaller than that of the supercap. more flat. The supercap will thus experience smaller state-of-charge changes and use only a fraction of its SOC range. Thus, a circuit comprising parallel connected supercapacitors and batteries, both supplying power to an electrical load, has the disadvantage that only a portion of the full SOC range of the supercapacitors can be utilized.

A super capacitor connected in series with a rechargeable power source as a booster

Another way to use a supercapacitor as a power booster is to connect the supercapacitor in series with a rechargeable power source. Since the discharge curve of a supercapacitor is linear, its entire voltage range can be utilized.

Since supercapacitors have low energy density and are more expensive per unit of energy storage than other rechargeable power sources, supercapacitors with lower nominal voltages can be used. Connecting an assembly of one or more supercapacitors in series with the rechargeable source means that the nominal voltage of the supercapacitor can be lower than the nominal voltage of the rechargeable source – eliminating the need to connect several supercapacitor cells in series to match the voltage of the rechargeable source – So fewer supercapacitor cells can be used.

Connecting the supercapacitor in series with the rechargeable source means that if the combined voltage across the supercapacitor and the rechargeable source is greater than or equal to a predetermined threshold voltage for powering the electrical load, the load handling means even if the voltage across the rechargeable source has dropped It can continue to operate when it falls below the predetermined threshold voltage. In practice, this means that the load handling unit can operate longer between charges at the charging station.

In the example given above, for a load processing device with a 48V Li-ion battery pack and a 48V electrical load, the predetermined threshold voltage is around 42.6V. With only the battery, the load processing unit needs to be charged once the battery voltage drops to 42.6V. However, with a 5V super capacitor in series with the battery, the load processing unit can continue to operate when the combined voltage 5V + 37.6V across the battery and super capacitor has dropped to a predetermined threshold voltage of 42.6V until the battery voltage drops to 37.6V.

2.7 or 5.4V supercapacitors are readily available commercially. Other voltages are also available.

For short-term peak power demands only

As noted above, the energy storage system of the load handling device must be able to provide sufficient power to the drive mechanism and/or lift drive assembly to complete the acceleration event. But a deceleration event does not have a constant power requirement.

The peak demand of the electrical load occurs only for a short period of time. Figure 36 plots the power requirements of the motors powering the wheels of the load handling device as the load handling device moves on top of the storage grid. It can be seen that the peak power demand occurs at about 1.1 seconds and lasts for less than 1 second. Therefore, the energy storage system only needs to provide maximum power for a short time. Supercapacitors are perfectly suited to provide this power boost because of their high power density and low energy density. Since the demand is only for a short period of time, high energy storage capacity is not required. Supercapacitors can assist in meeting power demands without adding significant additional mass or cost to the energy storage system.

The deceleration event, also see Fig. 36, is between about 1.3 seconds and 2 seconds. The power demand during this time is negative, meaning that the engine acts as a generator and recovers energy from the deceleration of the load handling device.

The energy storage system of the load handling device must be able to provide power to enable the gripper device to be lowered and raised by the lift drive assembly to retrieve or stack storage containers. As noted above, Figure 29 shows an example of the hoisting operation of a load handling device. It can also be seen from Figure 29 that the peak demand for electrical loads occurs only for a short period of time. The peak power demand for the first acceleration event occurred around 6.5 seconds and lasted just under 1 second. Therefore, the energy storage system only needs to provide maximum power for a short time. Supercapacitors are perfectly suited to provide this power boost because of their high power density and low energy density. Since the demand is only for a short period of time, high energy storage capacity is not required. Supercapacitors can assist in meeting power demands without adding significant additional mass or cost to the energy storage system.

Circuit diagram of a supercapacitor connected in series with a rechargeable power supply

FIG. 37 shows a simple circuit diagram of a supercapacitor 102 connected in series with a rechargeable power source 100 . The supercapacitor and the rechargeable power supply together supply power to the electrical load 104 . During normal operation, both the rechargeable power source 100 and the supercapacitor 102 supply power to the electrical load 104 .

Figure 37 shows a single battery cell 100, a single ultracapacitor 102, and a single electrical load 104 for ease of illustration only. The rechargeable power source 100 is not limited to a battery, and may include a plurality of battery cells connected in series and/or in parallel. Cells may be connected in series to increase voltage (eg, a battery with a nominal voltage of 48V may include 12 Li-ion cells in series, each with a maximum voltage of 4.2V), and/or in parallel to increase energy storage capacity. The supercapacitor 102 may include a plurality of supercapacitors connected in series or in parallel, the series connection increases the voltage, and the parallel connection increases the energy storage capacity. Electrical load 104 may include a plurality of electric motors or other components. For example, the electrical loads may include one or more motors as part of the lift drive assembly and one or more motors as part of the drive mechanism to drive the wheels of the load handling device.

FIG. 38 shows a circuit diagram when the rechargeable power source 100 includes a plurality of battery cells connected in series, the supercapacitor 102 includes a plurality of supercapacitor modules connected in series and parallel, and the electrical load 104 includes a plurality of motors connected in parallel.

Ground 105 is common; all ground components may be connected to the chassis of the load handling device.

Controlling Supercapacitor Charging

Controller 120 may be used to manage charging and discharging of ultracapacitor 102 . The controller may be configured to instruct the rechargeable power source 100 to charge the assembly of one or more supercapacitor modules when the voltage across the assembly of one or more supercapacitor modules is below a predetermined threshold supercapacitor recharging voltage .

The predetermined threshold supercapacitor recharge voltage may be defined sufficiently lower than the maximum rated voltage of the supercapacitor such that there is sufficient unused energy storage capacity to receive energy recovered from the deceleration event.

The DC-DC converter 122 can be used to convert the voltage between the rechargeable power source 100 and an assembly composed of one or more supercapacitor modules.

Controlling The capacitor directs the recovered energy to an assembly consisting of one or more supercapacitor modules.

A DC-DC converter can be used to convert the load voltage and the voltage between an assembly consisting of one or more supercapacitor modules. It may be the same as the DC-DC converter 122 used to convert the voltage between the rechargeable power source and the assembly of one or more supercapacitor modules.

An assembly of one or more ultracapacitor modules may be selected with a power rating sufficient to accommodate power recovered from the drive train and/or lift drive assembly during a deceleration event, and with an energy storage capacity sufficient to accommodate and store Energy recovered from a drive mechanism and/or lift drive assembly during one or more deceleration events. This ensures that all available recovered energy is captured and stored.

Figures 39 and 40 illustrate the control operation of the circuit. The controller 120 reads the voltage Vb across the rechargeable power supply and the combined voltage Vc across the rechargeable power supply and the supercapacitor. The voltage difference Vc – Vb between these two voltages is the voltage across the supercapacitor. The controller charges the supercapacitor if the voltage across the supercapacitor is below a predetermined threshold supercapacitor recharge voltage. The input current Iin to the controller can be supplied by a rechargeable power source, or it can be braking current recovered from the drive mechanism and/or lift drive assembly during a deceleration event. A DC-DC converter 122 may be used to convert the voltage of the input current to supply the supercapacitor with an appropriate voltage.

FIG. 39 shows the operation of the circuit when the rechargeable power source 100 is used to charge the supercapacitor 102 . The arrows in Figure 39 show the direction of current flow. The rechargeable power supply 100 supplies power to the electrical load 104 through the controller 120 and the DC-DC converter 122 , and also supplies power to the supercapacitor 102 .

FIG. 40 illustrates the operation of the circuit when the energy recovered from the electrical load 104 is used to charge the ultracapacitor 102 . The arrows in Figure 40 show the direction of current flow. The energy recovered from the electrical load 104 is provided to the ultracapacitor 102 through the controller 120 and the DC-DC converter 122 .

FIG. 41 shows a possible embodiment of the controller 120 and the DC-DC converter 122 in more detail. If the voltage Vc - Vb across the supercapacitor is below a predetermined threshold supercapacitor recharge voltage, the controller 120 sends a signal, which may be a square wave, to the base of the transistor 124 . Transistor 124 allows input current Iin to flow to ground 105 via the first coil of transformer 126 when activated. Current is introduced into the second coil of transformer 126 . This current passes through the rectifier 128 and is then used to charge the ultracapacitor 102 . The output voltage and current from the DC-DC converter 122 are monitored by the controller 120 measuring the voltage feedback Vfb and the current feedback Ifb.

Switch 130 may be used to protect ultracapacitor 102 from overcharging. The controller 120 can detect when the supercapacitor voltage is too high, such as when the supercapacitor voltage exceeds the maximum supercapacitor voltage, and can then operate a switch to disconnect the supercapacitor from the power source. The switch 130 is shown here between the controller 120 and the base of the transistor 124, but it should be understood that the switch can be located anywhere in the circuit to disconnect the ultracapacitor 102 from the power source.

Super capacitor protection circuit

During normal operation, the super capacitor 102 discharges and supplies power to the electrical load 104 . When the super capacitor is fully discharged, it will no longer be able to provide power. The super capacitor protection circuit 132 can be used to ensure that the super capacitor is not reverse charged once it is fully discharged. Reverse charging can damage the super capacitor.

FIG. 42 is a partial circuit diagram showing the supercapacitor protection circuit 132 bypassing the supercapacitor 102 . In normal operation, a supercapacitor is charged or partially charged and discharged as current passes through it. When the super capacitor is discharged, the super capacitor protection circuit 132 allows current to bypass the super capacitor instead of flowing through the super capacitor.

The supercapacitor protection circuit 132 that prevents reverse charging of the supercapacitor may include transistors. The transistors can be controlled by the super capacitor protection circuit controller 134 . When the voltage across the supercapacitor 102 drops below zero volts, the supercapacitor protection circuit controller 134 sends a signal to the base of the transistor 132 to turn it on and thus allow current to flow through the transistor 132 instead of through the supercapacitor 102 . The supercapacitor protection circuit controller 134 can be a separate device, or can be integrated into the same controller 120 that controls supercapacitor charging.

The rules used to control supercapacitors are summarized as follows:

1. If the voltage across the supercapacitor 102 is lower than a predetermined threshold supercapacitor recharging voltage, the controller 120 instructs the rechargeable power source 100 to charge the supercapacitor 102 through the DC-DC converter 122 .

2. If the voltage across the ultracapacitor 102 is below a predetermined threshold supercapacitor recharge voltage, the controller 120 directs any recuperated energy from the drive mechanism and/or lift drive assembly to the ultracapacitor 102 via the DC-DC converter 122 .

3. If the voltage across the supercapacitor 102 is lower than zero, the supercapacitor protection circuit controller 134 activates the supercapacitor protection circuit 132 to prevent the supercapacitor 102 from being reversely charged.

4. If the supercapacitor voltage is higher than the maximum supercapacitor voltage, then the controller 120 opens the switch 130 to disconnect the power supply from the supercapacitor and protect the supercapacitor 102 from overcharging.

Claims (26)

1. A load handling device (30) for lifting and moving one or more containers (10) stacked in a storage system comprising supports arranged above a stack (12) of said containers (10) in A grid frame (14) for pathways of grid graphics, said load handling means (30) comprising: i) a carrier body (32) housing a drive mechanism operatively arranged to move the load handling device ( 30); ii) lifting means comprising a lifting drive assembly and gripping means (39) configured in use to releasably grasp said container (10) and hold said container (10) The container (10) is lifted from the stack (12) into the container receiving space (40); wherein the lifting drive assembly and/or the drive mechanism includes at least one motor constituting an electrical load (104); iii) rechargeable power source (100); iv) Assemblies consisting of one or more supercapacitor modules (102); It is characterized in that the electric load (104) is connected across the two ends of the assembly composed of one or more supercapacitor modules (102), and the rechargeable power supply (100) is connected in parallel to the or an assembly composed of more than one supercapacitor module (102), such that the rechargeable power source (100) is configured to supply power to the assembly composed of one or more supercapacitor modules (102). 2. The load processing device (30) according to claim 1, further comprising a load DC-DC converter (110), the load DC-DC converter (110) is located in the (102) constitutes between the component and the electrical load (104). 3. The load processing device (30) according to claim 2, wherein the load DC- A DC converter is a boost converter. 4. The load handling device (30) according to any one of the preceding claims, further comprising a source DC-DC converter (108), the source DC-DC converter (108) being located at the rechargeable power source (100) and the component composed of one or more supercapacitor modules (102). 5. The load processing device (30) according to claim 4, wherein the source DC between the rechargeable power source (100) and the component composed of one or more supercapacitor modules (102) - The DC converter is a step-down converter. 6. The load processing device (30) according to any one of the preceding claims, wherein the controller (114) is configured to vary the supply from the rechargeable power source (100) to the one or more supercapacitor modules ( 102) The power of the constituent components. 7. The load processing device (30) according to claim 6, wherein the controller (114) is configured to instruct the rechargeable power source (100) to operate in the Power is supplied to the component composed of one or more supercapacitor modules (102) when the voltage of the composed component is lower than a predetermined supercapacitor target voltage threshold. 8. The load processing device (30) according to claim 6, wherein the predetermined supercapacitor target voltage threshold is lower than the maximum rated voltage of the assembly composed of one or more supercapacitor modules (102). 9. The load handling device (30) according to any one of claims 6-8, wherein the controller (114) is configured to instruct the rechargeable power source (100) for a predetermined The threshold current supplies power to the assembly composed of one or more supercapacitor modules (102). 10. The load processing device (30) according to any one of claims 6-8, wherein the controller (114) is configured to periodically connect the rechargeable power source (100) with the The assembly of one or more supercapacitor modules (102) is disconnected such that the rechargeable power source experiences a period of low current consumption during which no power is supplied to the assembly of one or more supercapacitor modules (102). 11. A load handling device (30) according to any preceding claim, further comprising an energy recovery circuit (112) to divert energy regenerated from the drive mechanism and/or the lifting device assembly to the An assembly composed of one or more supercapacitor modules (102), wherein the energy recovery circuit (112) includes diodes or transistors. 12. The load processing device (30) according to any one of the preceding claims, wherein the assembly composed of one or more supercapacitor modules (102) has a lower internal resistance than the rechargeable power supply (100) . 13. The load handling device (30) of any preceding claim, wherein the electrical load (104) comprises a first portion and a second portion, wherein the first portion of the electrical load (104) comprises a dynamic electrical load, And the second portion of the electrical loads (104) includes non-motive electrical loads (106). 14. The load processing device (30) of claim 13, wherein the rechargeable power source (100) is configured to supply power to the non-motive electrical load (106). 15. The load processing device (30) according to any one of the preceding claims, wherein the assembly composed of one or more supercapacitor modules (102) is configured as the main power supply of the load processing device (30), And the rechargeable power source (100) is configured as an auxiliary power source for powering the main power source. 16. The load processing device (30) according to claim 15, wherein the controller (114) is configured such that the voltage across the assembly consisting of one or more supercapacitor modules (102) is lower than a predetermined The supercapacitor voltage threshold indicates that the rechargeable power source (100) directly supplies power to the electric load (104). 17. The load processing device (30) according to any one of the preceding claims, wherein the components composed of one or more supercapacitor modules (102) are distributed on the carrier of the load processing device (30) A container receiving recess (40) in the main body (32) surrounds the outside of the recess (40), between the outer wall (42) and the inner wall (44) of the load handling device (30). 18. The load processing device (30) according to any one of the preceding claims, wherein the components composed of one or more supercapacitor modules (102) include capacitors, supercapacitors, supercapacitors, lithium capacitors, electrochemical dual Layer capacitance, electric double layer capacitance, pseudocapacitance or hybrid capacitance. 19. The load handling device (30) according to any one of the preceding claims, wherein the rechargeable power source (100) comprises a lithium-ion battery, a lithium-ion polymer battery, a lithium-air battery, a lithium-iron battery, a lithium iron phosphate battery , lead acid battery, nickel cadmium battery, nickel metal hydride battery, nickel zinc battery, sodium ion battery, sodium air battery, thin film battery, solid state battery or smart battery carbon foam based lead acid battery. 20. Storage system comprising a grid frame (14) supporting a stack (12) of containers (10) above a stack (12), aisles arranged in a grid pattern and a plurality of load handling units as defined in any preceding claim device (30). 21. The storage system according to claim 20, further comprising one or more supercapacitor charging stations located at grid positions above access points, wherein said load processing device (30) is composed of one or more An assembly composed of the above supercapacitor modules (102) is charged by one of the one or more supercapacitor charging stations during the lifting or lowering operation. 22. The storage system of claim 21, wherein the one or more supercapacitor charging stations are inductive supercapacitor charging stations. 23. The storage system according to any one of the preceding claims, wherein the controller (114) on the load processing device (30) is configured to instruct the The components charge the rechargeable power source (100). 24. The storage system according to any preceding claim, wherein the controller (114) is configured to instruct the one or more supercapacitor modules (102) to supply a predetermined threshold current for cell balancing to the A rechargeable power source (100) supplies power. 25. A fulfillment center comprising the storage system of any one of claims 20-24. 26. The fulfillment center of claim 25, wherein the temperature within the fulfillment center is any of the following temperatures: Ambient temperature of 4°C or higher; a refrigerated temperature of about 0° to about 4°C; A freezing temperature of about -25°C to about 0°C.

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